Previous research offers compelling evidence that leaders suffice to effect efficiency-enhancements on cooperation, yet the source of this effect remains unclear. To investigate whether leadership effects can be attributed exclusively to the common information that leaders provide to a group, irrespective of the source of that information, we design a public goods game in which non-binding contribution suggestions originate with either a human or computer leader. We find that group members decisions are significantly influenced by human leaders non-binding contribution suggestions, both when the leader is elected as well as when the leader is randomly chosen. A leader s suggestion becomes an upper bound for group member s contributions. Identical suggestions do not impact the group members decisions when they originate with a computer, thus supporting to the view that information provided by human leaders is uniquely able to establish welfare-enhancing norms.